import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Lily
 * Date: 2024-10-16
 * Time: 20:24
 */
public class test_3 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int b_x = in.nextInt();
            int b_y = in.nextInt();

            int x = in.nextInt() + 1;
            int y = in.nextInt() + 1;

            long[][] dp = new long[b_x + 2][b_y + 2];
            dp[0][1] = 1;
            for (int i = 1; i <= b_x+1; i++) {
                for (int j = 1; j <= b_y+1; j++) {
                    if (i != x && j != y && Math.abs(i - x) + Math.abs(j - y) == 3
                            || (i == x && j == y)) {
                        dp[i][j] = 0;
                    } else {
                        dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                    }
                }
            }
            System.out.println(dp[b_x + 1][b_y + 1]);
        }
    }
}
